1. Field of the Invention
The present invention relates to electrical connectors for IC cards.
2. Description of the Related Art
Japanese U.M. patent application Kokai No. 61-131081 discloses a thin-type electrical connector having a foolproof structure that allows the connector to fit into only a specific connector. It is desirable that the connector is able to fit into as many different connectors as possible. Consequently, the foolproof structure should be flexible. The foolproof structure has a number of key grooves extending laterally on the upper and lower fitting edges. A planar key is inserted into a given position and number of key grooves that prevent plugging wrong connectors. This foolproof structure is convenient because by selecting the key position and number it is possible to provide a variety of foolproof structures without difficulty.
However, since the key groove and the key are provided on the upper and lower fitting edges, the thickness of the connector increases by that much. Consequently, it is hardly possible to provide a connector useful for IC cards which have a thickness of about 3 mm because the thickness of the key is one to two millimeters.